Method of stabilizing a plastic aerosol container

ABSTRACT

A plastic aerosol container includes a main body portion that is constructed and arranged to withstand aerosol pressurization within a range that is about 50-300 psig. The plastic aerosol container also includes a finish portion that is unitary with the main body portion. The finish portion may be threaded or unthreaded. The finish portion has a side wall, an upper sealing surface, at least one helical thread and a support ledge beneath the helical thread. Reinforcement structure is positioned beneath the support ledge for reinforcing the finish portion against deformation due to the pressurization. A method of stabilizing a plastic aerosol container is also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates broadly to the field of containers that areadapted to hold highly pressurized contents, such as aerosol mixtures,and more particularly to a blow molded plastic aerosol container havinga finish portion that is constructed and arranged to provide maximumresistance to deformation and stress cracking at high internalpressures.

2. Description of the Related Technology

Aerosol containers have conventionally been fabricated from metal, andare conventionally formed as a cylindrical tube having upper and lowerend closures. The bottom end closure is typically shaped as a concavedome, and the upper end closure typically includes a manually actuatablevalve for dispensing the pressurized aerosol contents of the container.

Metallic containers have certain inherent disadvantages, such as atendency to rust over time and to scratch surfaces with which they maycome into contact.

Efforts have been made in the past to develop plastic aerosolcontainers, but have encountered difficulties, mainly relating tocontrolling the deformation of the plastic material as a result of thesignificant internal pressurization that is necessary in an aerosolcontainer. Aerosol containers commonly require internal pressures of themagnitude of 50-300 psi, which is significantly greater than pressuresthat are typically encountered in other packaging applications for whichplastic material has been used, such as the packaging of carbonatedbeverages. Accordingly, design considerations for plastic aerosolcontainers are quite different than they are for lower pressurepackaging applications such as plastic beverage containers.

One common type of plastic container is fabricated from a material suchas polyethylene terephthalate (PET) and is manufactured from aninjection molded preform having a threaded finish portion using thereheat stretch blow molding process. While such containers hold somepromise for aerosol applications, they are susceptible to stresscracking in the finish portion while under pressurization. In addition,the finish portion of such containers has a tendency to deform when thecontainer is pressurized, possibly resulting in a loss of sealingintegrity between the container and the aerosol dispensing closure.

A need exists for an improved blow molded plastic aerosol container thatis less susceptible to stress cracking and deformation in the finishregion than are conventional blow molded plastic containers.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an improvedblow molded plastic aerosol container that is less susceptible to stresscracking and deformation in the finish region than are conventional blowmolded plastic containers.

In order to achieve the above and other objects of the invention, aplastic aerosol container according to a first aspect of the inventionincludes a main body portion that is constructed and arranged towithstand aerosol pressurization within a range that is about 50-300psig. The plastic aerosol container further includes a finish portionthat is unitary with the main body portion. The finish portion has aside wall, an upper sealing surface and a support ledge. The plasticaerosol container further includes reinforcement structure positionedbeneath the support ledge for reinforcing the finish portion againstdeformation due to the pressurization.

A method of stabilizing an aerosol container of the type that has aplastic container having a finish portion with a side wall, an uppersealing surface and a support ledge according to a second aspect of theinvention includes steps of forming reinforcement structure beneath thesupport ledge for reinforcing the finish portion against deformation dueto pressurization; installing an aerosol dispensing closure onto thefinish portion; and pressurizing the container with an aerosol mixturethat is pressurized within a range that is about 50-300 psig.

These and various other advantages and features of novelty thatcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to the accompanying descriptive matter, inwhich there is illustrated and described a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary cross-sectional view taken along lines 1-1 inFIG. 2;

FIG. 2 is a top plan view of an aerosol container assembly that isconstructed according to a preferred embodiment of the invention;

FIG. 3 is a bottom plan view of the aerosol container assembly that isshown in FIG. 2;

FIG. 4 is a side elevational view of the finish portion of the aerosolcontainer assembly that is shown in FIG. 2;

FIG. 5 is a cross-sectional view taken along lines 5-5 in FIG. 3;

FIG. 6 is a cross-sectional view taken along lines 6-6 in FIG. 3;

FIG. 7 is a diagrammatical view depicting the manufacture of an aerosolcontainer according to an alternative embodiment of the invention;

FIG. 8 is a diagrammatical view depicting an aerosol closure assemblyaccording to the preferred embodiment of the invention;

FIG. 9 is a fragmentary cross-sectional view taken through a preformthat is constructed according to the preferred embodiment of theinvention;

FIG. 10 is a flowchart depicting a method according to the preferredembodiment of the invention;

FIG. 11 is a flowchart depicting another method according to thepreferred embodiment of the invention; and

FIG. 12 is a fragmentary cross-sectional view taken through an aerosolcontainer assembly that is constructed according to an alternativeembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, wherein like reference numerals designatecorresponding structure throughout the views, and referring inparticular to FIG. 1, an aerosol container assembly 10 that isconstructed according to a preferred embodiment of the inventionincludes a plastic aerosol container having a main body portion 12 thatis constructed and arranged to withstand aerosol pressurization within arange of about 50 psig to about 300 psig. More preferably, the main bodyportion 12 is constructed and arranged to withstand aerosolpressurization within a range of about 90 psig to about 180 psig.

Plastic aerosol container 10 is preferably fabricated from a plasticmaterial such as polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), acrilonitrile (AN), polycarbonate (PC), polyamide(Nylon), or a blend containing some combination of the same from aplastic preform using a conventional blow molding process such as thereheat stretch blow molding process.

In the preferred embodiment, container 10 is fabricated from a highintrinsic viscosity polyethylene terephthalate material, which mostpreferably has an intrinsic viscosity that is substantially within arange of about 0.76 to about 0.95.

Container 10 preferably has an average wall thickness in the main bodyportion 12 that is substantially within a range of about 0.018 inch toabout 0.022 inch, permitting it to withstand aerosol pressures.

The aerosol container 10 further preferably includes a threaded finishportion 14 that is unitary with the main body portion 12 and that has atleast one helical thread 16 defined thereon for receiving an aerosoldispensing closure assembly or a closure that is designed to accept anaerosol fitment. Finish portion 14 further includes a support ledge 18beneath the helical thread 16, which is used to help convey thecontainer 10 during manufacture and filling. The support ledge 18 has afirst maximum outer diameter D_(L), as is best shown in FIG. 1.

The support ledge 18 is preferably constructed so that it has asubstantially circular circumference as viewed in top plan. In thepreferred embodiment, the outer circumference of the support ledge 18includes a pair of small recesses 24, which are used for registering theclosure fitment to the finish of the container 10 during the cappingprocess.

The threaded finish portion 14 further includes reinforcement structurethat is positioned beneath the support ledge for reinforcing the finishportion 14 against deformation due to the pressurization within theaerosol container 10. In the preferred embodiment, the reinforcementstructure includes at least one secondary flange 20, which is positionedbeneath the support ledge 18 on the threaded finish portion 14. Thesecondary flange 20 is preferably constructed so that it has an outercircumference that is noncircular in at least one location, so that itmay be engaged during a capping operation to prevent rotation of thecontainer 10 during capping. The secondary flange 20 is preferablyunitary with the side wall of the finish portion 14.

The secondary flange 20 in the preferred embodiment is fabricated usingan injection molding process together with the rest of a plastic preform50, shown in FIG. 9, which is used to manufacture the aerosol container10 using a reheat stretch blow molding process. The plastic preform 50includes a body portion 52.

In an alternative embodiment of the invention, shown in FIG. 7, a blowmolded aerosol container 30 includes a threaded finish portion 32 havinga support ledge 34 and a secondary flange 36. In this embodiment, thereinforcement structure is embodied as a secondary flange 36 that isfabricated in an upper part of the main body portion 12 during the blowmolding process through the use of a mold 38, and is not part of thepreform that is used to manufacture the container 30.

In another alternative embodiment of the invention, anti-rotationfeatures could be incorporated into the support ledge of the finishportion without the provision of a secondary flange. For example, thesupport ledge could be provided with two or more flat surfaces, groovesor notches on the underside of the support ledge or one or more lugs ornotches on the top surface of the support ledge.

The secondary flange 20 is preferably constructed so as to have a secondmaximum outer diameter D_(S), which is not substantially greater thanthe first maximum outer diameter D_(L) of the support ledge 18.Preferably, the second maximum outer diameter D_(S) of the secondaryflange 20 is substantially the same as the first maximum outer diameterD_(L) of the support ledge 18.

Preferably, the secondary flange 20 has at least one substantially flatportion defined thereon that may be engaged by a capping machine inorder to prevent relative rotation of the container 10 with respect tothe capping machine during the capping process. As is best shown in FIG.3, the secondary flange 20 preferably has four flat portions 22 that areevenly spaced around the circumference of the secondary flange 20.

As FIG. 1 shows, an annular space 28 is defined between the supportledge 18 and the secondary flange 20. Annular space 28 has a minimumvertical dimension H_(S) that is preferably at least about 1 mm, andthat is more preferably at least about 1.5 mm.

The aerosol container assembly further includes an aerosol dispensingclosure 40, which is diagrammatically shown in FIG. 8. Aerosoldispensing closure 40 preferably includes an apron or collar 42 that isadapted to be threaded onto and sealed to the threaded finish portion14. Securing structure is preferably provided in order to prevent theconsumer from unscrewing the aerosol dispensing closure 40 from thecontainer 10, which in the preferred embodiment is a glue material thatis applied to apron 42 of the aerosol closure 40 and the finish portion14.

The aerosol dispensing closure 40 preferably includes a metallic insert44 having a central opening in which an aerosol dispensing valve 46 ispositioned.

A method of assembling an aerosol container assembly according to thepreferred embodiment of the invention is shown diagrammatically in FIG.10. It includes providing a container 10 as described above having athreaded finish portion 14, a support ledge 18 positioned beneath thethreaded finish portion and a secondary flange 20 positioned beneath thesupport ledge 18. The secondary flange 20 preferably has at least onenoncircular portion.

The collar 42 of the aerosol dispensing closure 40 is then installed byscrewing it onto the threaded finish portion 14, preferably by using acommercial capping machine. During the capping process, the container 10is secured against rotation relative to the capping machine byengagement of a portion of the capping machine with the noncircularportion of the secondary flange 20. The collar 42 of the aerosoldispensing closure 40 is preferably screwed onto the threaded finishportion at a torque that is substantially within a range of about 15in-lbs to about 50 in-lbs. The container 10 is then filled with product,after which the metallic insert 44 of the aerosol dispensing closureassembly 40 is applied to the collar and the container is pressurizedwith an aerosol mixture at a range of pressurization that issubstantially between about 50 psig to about 300 psig, and morepreferably substantially within a range of about 90 psig to about 180psig using known aerosol pressurization processes and equipment.

The aerosol mixture preferably includes a propellant, which could be aliquefied gas propellant or a compressed or soluble gas propellant.Liquefied gas propellants that could be used include hydrocarbonpropellants such as propane, isobutene, normal butane, isopentane,normal pentane and dimethyl ether, and hydrofluorocarbon propellantssuch as difluoroethane (HFC-152a) and tetrafluoroethane (HFC-134a).Compressed and soluble gas propellants that could be used include carbondioxide (C02), nitrous oxide (N20), nitrogen (N2) and compressed air.

A method of stabilizing an aerosol container according to the preferredembodiment of the invention, shown diagrammatically in FIG. 11, includesfabricating an aerosol container 10 that is constructed as describedabove, with the reinforcement structure formed beneath the support ledge18 for reinforcing the finish portion 14 against deformation due topressurization. An aerosol dispensing closure 40 is then installed byscrewing onto the threaded finish portion 14 at the preferred torquethat is described above. The plastic aerosol container 10 is thenpressurized with an aerosol mixture within a range of pressurizationthat is preferably about 50-300 psig. When under pressurization, thereinforcement structure prevents deformation of the finish portion 14,particularly the upper sealing surface of the finish portion 14 thatbears against the underside of the aerosol dispensing closure 40. Thishelps ensure the integrity of the aerosol container assembly againstloss of pressurization, and increases the potential shelf life of theaerosol container assembly.

An aerosol dispensing container 60 according to a alternative embodimentof the invention is depicted in FIG. 12. Aerosol dispensing container 60includes an unthreaded finish portion 62 having a support ledge 18 and asecondary flange 20, each of which is preferably constructed identicallyto those described above with reference to the previous embodiment.Unthreaded finish portion 62 further includes an upper bead 64 definingan upper rim of the container 60, and an undercut 66 on an outer surfaceof the finish portion 62. An aerosol valve assembly 68 has a flangeportion 70 that is designed to be installed onto the finish portion 62by crimping the outer circumferential edge of the flange portion 70about the upper bead 64 and the undercut 66.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

What is claimed is:
 1. A method of stabilizing an aerosol container ofthe type that has a plastic container having a main body portion and afinish portion, the finish portion having a side wall and an uppersealing surface, the method comprising: forming on the finish portion asecurement structure extending outwardly from the side wall, a supportledge separate from and beneath the securement structure, and areinforcement structure separate from and beneath the support ledge forreinforcing the finish portion against deformation due topressurization; installing an aerosol dispensing closure on to thefinish portion; and pressurizing the container with an aerosol mixturethat is pressurized within a range that is about 50-300 psig.
 2. Amethod of stabilizing an aerosol container according to claim 1, whereinthe step of forming the reinforcement structure is performed by formingthe reinforcement structure on the finish portion.
 3. A method ofstabilizing an aerosol container according to claim 2, wherein thereinforcement structure comprises a secondary flange that is unitarywith the side wall of the finish portion.
 4. A method of stabilizing anaerosol container according to claim 3, wherein the secondary flange isfabricated by injection molding.
 5. A method of stabilizing an aerosolcontainer according to claim 1, wherein the reinforcement structure isfabricated by blow molding.
 6. A method of stabilizing an aerosolcontainer according to claim 5, further comprising securing the aerosoldispensing closure to the finish portion using securement structure. 7.A method of stabilizing an aerosol container according to claim 1,wherein the finish portion and the main body portion are fabricated fromthe material comprising polyethylene terephthalate.
 8. A method ofstabilizing an aerosol container according to claim 1, wherein the mainbody portion is constructed of plastic and capable of withstandingaerosol pressurization within a range from about 50 psig to about 300psig.
 9. A method of stabilizing an aerosol container according to claim1, wherein the main body portion is constructed of plastic and capableof withstanding aerosol pressurization within a range from about 90 toabout 180 psig.
 10. A method of stabilizing an aerosol containeraccording to claim 1, wherein the container has a wall thickness in therange from about 0.018 inch to about 0.022 inch.
 11. A method ofstabilizing an aerosol container according to claim 1, wherein thesecurement structure comprises a threaded portion.
 12. A method ofstabilizing an aerosol container according to claim 11, wherein thefinish portion and the main body portion are fabricated from a materialcomprising at least one of the following: polyethylene terephthalate,polyethylene naphthalate, acrilonitrile, polycarbonate, polyamide, or ablend thereof.
 13. A method of stabilizing an aerosol containeraccording to claim 12, wherein the material has a viscosity ranging fromabout 0.76 to about 0.95.